package com.itheima.utils;

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;

/**
 * 根据出生日期转年龄工具类
 */
public class AgeUtils {

    /**
     * 把字符串出生日期转换为日期格式
     *
     * @param strDate
     * @return
     * @throws ParseException
     */
    public static Date parse(String strDate) throws ParseException {
        SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd");
        return simpleDateFormat.parse(strDate);
    }

    /**
     * 计算年龄
     *
     * @param birthDay
     * @return
     * @throws Exception
     */
    public static int getAge(Date birthDay) throws Exception {
        Calendar cal = Calendar.getInstance();
        if (cal.before(birthDay)) { //出生日期晚于当前时间，无法计算
            throw new IllegalArgumentException(
                    "你是未来人吗");
        }
        int yearNow = cal.get(Calendar.YEAR); //当前年份
        int monthNow = cal.get(Calendar.MONTH);//当前月份
        int dayOfMonthNow = cal.get(Calendar.DAY_OF_MONTH);//当前日期
        cal.setTime(birthDay);
        int yearBirth = cal.get(Calendar.YEAR);
        int monthBirth = cal.get(Calendar.MONTH);
        int dayOfMonthBirth = cal.get(Calendar.DAY_OF_MONTH);
        int age = yearNow - yearBirth;   //计算整岁数
        if (monthNow <= monthBirth) {
            if (monthNow == monthBirth) {
                if (dayOfMonthNow < dayOfMonthBirth) age--;//当前日期在生日之前，年龄减一
            } else {
                age--;//当前月份在生日之前，年龄减一
            }
        }
        return age;
    }

    //测试
    public static void main(String[] args) {
        try {
            int age = getAge(AgeUtils.parse("1995-12-25")); //由出生日期获得年龄
            System.out.println("age:" + age);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}
